Can I pass multiple functions to an http.createServer in NodeJS?

Question

I'm completely new to server development and NodeJS, so my apologies if this question sounds stupid or if such a question already exists.

I was following a simple NodeJS tutorial and building a simple "Hello World" server. I noticed that http.createServer took only one function as its argument.

http.createServer(function(req,res) {
 res.writeHead(200, {'Content-Type' : 'text/html'});
 res.end("Hello World");
}.listen(8080);

I tried passing another function to it like the following:

var http = require('http');

http.createServer(function(req,res) {
    res.writeHead(200, {'Content-Type':'text/html'});
    res.end("Hello World");
},
function (req, res) {
    res.write("Blahblah");
    res.end();
}
).listen(8080);

But hitting localhost:8080 returned only Hello World.

So I was wondering if I could pass multiple functions to it and if not, then why.

Thank you for your time

Answer 1

You cannot pass multiple functions. If you want multiple listeners for incoming requests, you can just register another listener for incoming requests:

const server = http.createServer(function(req,res) {
    res.writeHead(200, {'Content-Type' : 'text/html'});
    res.end("Hello World");
}.listen(8080);

// add additional listener
server.on('request', function(req, res) {
    if (req.url === "/goodbye") {
        res.writeHead(200, {'Content-Type' : 'text/plain'});
        res.end("goodbye");
    }       
});  

Note: right from the doc for http.createServer(), it says this about the function parameter passed to http.createServer():

http.createServer([options][, requestListener])

The requestListener is a function which is automatically added to the 'request' event.

Doc for the request event is here.

---

As others have said, it is pretty rare to use a plain http server like this because some simple routing is nearly always helpful and a lightweight framework like Express offers very useful features without really getting in the way of anything you might want to do. In the case of Express, you'd use code like this:

const express = require('express');
const app = express();

// define handler for /goodbye URL
app.get('/goodbye', function(req, res) {
    res.send("goodbye");
});

// define handler for /hello URL
app.get("/hello", function(req, res) {
    res.send("hello");
});

const server = app.listen(8080);

Here express, keeps a list of the URLs that you wish to handle and then listens for each incoming request, compares it against the URLs you wanted to handle and calls the appropriate route handler. It has lots of other features for routing too such as middleware, wildcards, parameterized URLs, etc...